|Prototype Model Unit XJ-3|
|Age||Unknown (Older than XJ-9)|
|Occupation||Superhero/crime fighter (When awake)|
|Likes||Helping people, saving the world|
|Dislikes||The Cluster, Smytus, falling apart uncontrollably|
|Family|| Nora Wakeman (creator/mother)|
XJ-1, XJ-2 (early prototypes/sisters), XJ-4, XJ-5, XJ-6, XJ-7, XJ-8, XJ-9 (later sisters)
Wisteria Wakeman (aunt)
Glenn Wakeman (cousin)
|Friends||Brad Carbunkle, Tuck Carbunkle|
|First appearance||"Sibling Tsunami"|
Prototype Model Unit XJ-3 is a small, cute XJ prototype robot. XJ-3 is not very stable, and, thus, falls apart when she hits things. In terms of robotic development, she represents a toddler who is just beginning to learn how to walk. Her biggest weakness is that her body does not resist much strength, which causes it to be easily disassembled.
She appears as a smaller version of Jenny with only one eye, two pincers as hands, and rounder.
- Sibling Tsunami (Her first appearance)
- Sister Sledgehammer
- Agent 00' Sheldon (No Lines)
- Escape from Cluster Prime (Brief Cameo)
- Labor Day (Brief Cameo)
- Because she can't talk, XJ-3 is the only XJ robot to not have a voice actor.
- She is the one to get fixed a lot by Nora, or gets 'cleaned up' by XJ-4.